The project is designed to elucidate the role of xenobiotic-metabolizing enzymes in skin as mediators of the toxicity of environmental agents. Mixed-function oxidases (including aryl hydrocarbon hydroxylase), glutathione S-transferase and UDP-glucuronosyotransferase activities are measured in whole skin, epidermal cells or subcellular fractions of epidermal cells from hairless mice (Hrs/J). Epidermal cell types high in xenobiotic-metabolizing activity and/or cytochrome P-450 content are being identified. Changes in xenobiotic metabolism and/or in the content of mixed-function oxidase components after exposure (topical or systemic) of mice to ultraviolet radiation, polycyclic hydrocarbons, chlorinated hydrocarbons, steroids, etc., are being investigated.